More Battles among Licensed Occupations:
Estimating the Effects of Scope of Practice
and Direct Access on the Chiropractic,
Physical Therapist, and Physician Labor Market
Edward J. Timmons, Jason M. Hockenberry,
and Christine Piette Durrance
MERCATUS RESEARCH
Edward J. Timmons, Jason M. Hockenberry, and Christine Piette Durrance. “More Battles
among Licensed Occupations: Estimating the Effects of Scope of Practice and Direct
Access on the Chiropractic, Physical Therapist, and Physician Labor Market.” Mercatus
Research, Mercatus Center at George Mason University, Arlington, VA, September 2016.
ABSTRACT
Primary-care physicians, chiropractors, and physical therapists (PTs) may all
potentially treat patients experiencing back and neck pain—a $300 billion market. In this paper, we examine how state-level changes in chiropractic scope of
practice and PT direct access to patients influence the wages, hours worked,
and employment of each practitioner. Our results suggest that expansions in
chiropractic scope of practice are associated with an increase in average chiropractor wages and a slight reduction in the average hours chiropractors work
per week. We find little evidence that PT direct access has affected the labor
market for any of the three studied practitioners.
JEL codes: J44
Keywords: occupational licensing, scope of practice, health care, primary care
Copyright © 2016 by Edward J. Timmons, Jason M. Hockenberry, and
Christine Piette Durrance
and the Mercatus Center at George Mason University
Release: September 2016
The opinions expressed in Mercatus Research are the authors’ and do not represent official positions of the Mercatus Center or George Mason University.
T
he number of workers directly affected by occupational licensing
has grown from about 4 percent in the 1950s to about 29 percent
as of 2006 (Kleiner and Krueger 2010). The issue has attracted
attention from policymakers at both the state and federal levels
(US Treasury 2015). Licensing statutes restrict the practice of a profession to
only those individuals who have met a specific set of requirements (typically
minimum training levels and examinations). In theory, restricting the supply
of potential entrants into a profession through licensing may increase a professional’s earnings. Recent literature suggests this effect is important when a
broad profession includes two types of service providers that might compete
for clients (Perry 2009; Kleiner et al. 2014) and when one service provider can
influence the licensing of the other (Kleiner and Won Park 2011; Kleiner 2013).1
In this paper, we focus on the practice of medicine, chiropractic, and physical therapy, which are each licensed in all 50 states. Licensing statutes typically
specify the tasks that license holders are allowed to perform. Chiropractors, physical therapists (PTs), primary-care physicians, and (in complex cases) orthopedic
surgeons all have treatment modalities for back and neck pain. Each profession
has historically had a different philosophy of the sources of pain and its management, different evidence bases supporting each approach’s efficacy, and different views on the quality of each profession’s evidence. Stated simply, there has
1. Some restrictions imposed through occupational licensing have drawn the recent attention of
the antitrust authorities. The Supreme Court recently decided N.C. Bd. of Dental Exam’rs v. Fed.
Trade Comm’n, 717 F.3d 359 (4th Cir. 2013), aff’d, 135 S. Ct. 1101 (2015)). In response to the rise in
teeth-whitening services provided by nondentists, the North Carolina Dental Board sent cease-anddesist letters to nondentist teeth whiteners, indicating that they were practicing illegally and should
stop offering these services because teeth whitening is the practice of dentistry. The Federal Trade
Commission (FTC) challenged the Board’s conduct, alleging that their actions led to higher prices,
reduced consumer choice, and suppressed competition. The US Court of Appeals for the Fourth
Circuit sided with the FTC. The Supreme Court ruled that the board failed the “state action doctrine”
requirement of active state supervision because the board comprises members that are active participants in the occupation that it regulates.
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“In theory, the
extent to which
these providers
are complements
or substitutes
should be evident
from observable
changes in their
labor supply and
wages arising
from changes in
the law.”
been historical animosity among the professions. Animosity between chiropractors and physicians has been driven
by the validity of the science, whereas in the case of physical therapists and physicians, it is an issue of professional
subordination akin to that of dentists and dental hygienists
studied by Kleiner and Won Park (2011). This historical animosity, coupled with different philosophies of treatment,
has led to substantial competition for patients seeking relief
from back and neck pain, a market which involves approximately $300 billion in spending per year (Armstrong 2011).
Because of the increasing number of individuals seeking relief from back and neck pain (Freburger et al. 2009;
Waterman, Belmont, and Schoenfeld 2012) and related musculoskeletal conditions, chiropractors and PTs now have an
important role in the market for medical services directed
at treating these conditions. Furthermore, as patients come
to trust these nontraditional providers, there has also been
an expanding role, at least in the case of chiropractic, for the
delivery of other medical services (e.g., allergy treatments)
typically provided by primary-care physicians.
Whether these providers serve as complements to
or substitutes for physicians depends on perspective. The
nature of the relationship between these professions is partially driven by the legal environment. Specifically, scopeof-practice and direct-access laws define the boundaries
between the professions. Variation in these laws across
states and over time allows for an empirical examination of
the relationship between all three providers. In theory, the
extent to which these providers are complements or substitutes should be evident from observable changes in their
labor supply and wages arising from changes in the law.
We examine how and to what extent state-level
scope of practice for chiropractors and direct-access laws
for PTs impact the earnings, hours worked, and employment of chiropractors, PTs, and physicians. We match
state-level scope-of-practice data obtained from the Federation of Chiropractic Licensing Boards and data on the
presence of direct-access laws from the American Physical Therapy Association (APTA) with 1970–2000 census
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data and 2001–2010 American Community Survey (ACS) data. Our results
suggest that more permissive scope-of-practice laws increase chiropractor
wages. We find no evidence that direct-access laws affect PT or chiropractor wages. Overall, the net effect of these laws for consumers may be positive
since consumers have access to a wider choice of providers (PTs, physicians,
and chiropractors) at potentially lower cost.2 Finally, we test for the possibility of policy endogeneity by examining whether growth in professional wages
or practitioner supply predicts the adoption of policy in the next 10 years. We
find limited evidence of policy endogeneity for scope-of-practice laws and no
evidence for direct-access laws.
I. BRIEF HISTORY AND BACKGROUND
A. Brief History of Chiropractic Licensing and Overview of
Scope of Practice
For much of its history, chiropractic has been at odds with the allopathic medical profession.3 The origins of the practice of chiropractic can be traced to
Daniel David Palmer in the United States in 1886. Palmer offered “magnetic
healing” with his hands as a substitute to the services provided by physicians
in Iowa. Chiropractic practitioners in the early nineteenth century were often
prosecuted for violating state allopathic or osteopathic licensing laws. Palmer
was one of the first individuals in the United States to be found guilty of practicing medicine without a license and served 23 days in prison in 1906 (Keating,
Cleveland, and Menke 2004).
As chiropractic expanded at the beginning of the twentieth century,
the Flexner report (published in 1910) addressed concerns over heterogeneity in the training and practice of medicine in the United States and Canada.
Although chiropractic medicine was not a focus of his report, it was mentioned
in a negative light:
2. According to data from the American Chiropractic Association, American Physical Therapist
Association, and American Medical Association, a chiropractic visit costs about $65, a PT visit costs
$80, a primary-care visit costs about $100, and an orthopedist visit costs about $232.
3. Allopathic medicine, sometimes referred to as Western or evidence-based medicine, has traditionally been the majority philosophy and source of training for physicians in the United States.
Osteopathic medicine, which takes a more “holistic” approach, has come into the mainstream more
recently. Importantly, it includes some role for manual spinal manipulation, which is a core treatment modality among chiropractors, though there are differences in the training and philosophy
of the two groups. Other divisions in medicine include naturopathy and homeopathy, but these are
beyond the scope of this paper owing to data limitations within the census and ACS.
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The chiropractics, the mechano-therapists, and several others are not medical sectarians, though exceedingly desirous of
masquerading as such; they are unconscionable quacks, whose
printed advertisements are tissues of exaggeration, pretense,
and misrepresentation of the most unqualifiedly mercenary
character (Flexner 1910).
In order to establish chiropractic as a viable and legal alternative to physician
services, chiropractors began lobbying for licensing legislation (Wardwell
1992). Kansas was the first state to license chiropractors in 1913. Over the next
decade, 26 additional states adopted licensing legislation. By the end of 1933,
all but 11 US jurisdictions had passed licensing statutes. The final state to pass
a statute was Louisiana in 1974 (Wardwell 1992).
To combat encroachment by chiropractors and other nontraditional medical practitioners in the market for physician services, the American Medical
Association (AMA) and regional and state medical societies lobbied for “basic
science” statutes that required all medical practitioners, including chiropractors,
to pass a common entry exam consisting of questions on anatomy, bacteriology,
and physiology (Keating, Cleveland, and Menke 2004). The laws were quite successful in blocking entry of aspiring chiropractors. For example, between 1929
and 1950, not a single new chiropractor was licensed in Nebraska (Metz 1965).
Chiropractic services were also originally excluded from Medicare coverage.
Because of the view that chiropractic practice was based on dubious science, the AMA actively fought the expansion of chiropractic care and barred any
association of physicians with chiropractors and other practitioners of “unscientific” healing. In 1963, the AMA formed a “Committee on Quackery,” which
attempted to eliminate chiropractors. But chiropractors eventually fought back,
beginning with intense and successful lobbying efforts for Medicare to cover
some chiropractic services beginning in 1973 and a landmark antitrust lawsuit
filed in 1976.4 By 1980, the “basic science test” requirement was repealed in all
states, and in 1990 the AMA was found to have violated the Sherman Act.5 Nevertheless, the influence of physicians in shaping chiropractic licensing laws
remains visible in the scope-of-practice sections of these statutes. Further,
recent evidence suggests that, because they want to protect market share, physicians are reluctant to accept chiropractic as a viable substitute (Kelner et al.
2004), and willingness to make referrals to chiropractors still appears limited
4. Wilk v. Am. Med. Ass’n, 719 F.2d 207 (7th Cir. 1983).
5. Wilk v. Am. Med. Ass’n, 895 F.2d 352 (7th Cir. 1990).
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(Greene et al. 2006). The scope-of-practice section of a licensing statute specifies the tasks licensees are allowed to perform. If physicians are able to successfully prevent chiropractors from performing certain procedures, they may
conceivably be able to defend their market share. The market share of physician
visits related to back and neck pain is economically meaningful, with recent
estimates suggesting 5 out of every 100 adults aged 18–64 seek nonoperative care
for back and neck pain in a given year (Feuerstein, Marcus, and Huang 2004).
Chiropractic scope-of-practice laws vary tremendously from state to
state. There is no complete source of information on scope of practice for each
state, but the Federation of Chiropractic Licensing Boards conducts a survey of
licensing regulations for each state that does contain some important information on chiropractic scope of practice.6 Utilizing data furnished by the Federation of Chiropractic Licensing Boards, we identify phlebotomy (i.e., the process
of inserting a needle into a vein), advice and recommendations on the use of
proprietary drugs, and physiotherapy (i.e., physical therapy) as three key elements of scope of practice that have the greatest potential to influence the market for chiropractors, physical therapists, and physicians. Table 1 presents data
on important changes to chiropractic scope of practice in each state. Beginning
in 1994, six states (Arkansas, Colorado, Iowa, Illinois, Nevada, and Wisconsin)
began to allow chiropractors to perform phlebotomy. In the 1990s, 24 states
began to allow chiropractors to discuss the use of proprietary drugs with their
patients, and 34 states broadened the scope of practice of chiropractors also to
include physiotherapy. Phlebotomy is a routine medical service, but it is nonetheless an important diagnostic procedure because it opens the door to performing blood tests and other routine medical procedures. Patients often seek
advice on proprietary drugs from primary-care physicians and obtain physiotherapy services from physical therapists. Granting chiropractors the ability to
perform phlebotomy, discuss proprietary drug treatments with patients, and
perform physiotherapy may serve as a signal to the patient of provider quality
and legitimacy; patients may be more likely to use chiropractic services in the
future or may share the information with peers. In addition, chiropractors will
be able to deliver a broader scope of services to patients. There are significant
regional differences in chiropractic use among older adults (Weigel et al. 2010).
Unfortunately, there are no data that track chiropractic utilization at the state
level over our period of study.
6. There have been attempts to gather nearly complete data on scope of practice (for instance, Lamm
and Wegner (1989) and Lamm and Pfannenschmidt (1999)), but unfortunately the data are only available for 1988, 1992, and 1998.
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TABLE 1. CHANGES TO CHIROPRACTOR SCOPE OF PRACTICE IN THE UNITED STATES
PANEL A. ALLOWING PHLEBOTOMY
State
Year
AR
1995
AZ
1995
CO
1994
IA
1994
IN
1997
NV
1994
WI
1994
Source: FCLB (1991–2010).
PANEL B. ALLOWING ADVICE ABOUT PROPRIETARY DRUGS
State
Year
State
Year
State
Year
AL
1996
MD
1997
OH
1997
CO
1995
MI
1997
OK
1991
CT
1997
MO
1997
OR
1997
FL
1998
MS
1997
PA
1997
1998
IA
1995
NE
1997
RI
KS
1997
NM
1997
TN
1998
LA
1997
NV
1995
UT
1999
MA
1997
NY
1995
WV
1995
Source: FCLB (1991–2010).
PANEL C. ALLOWING PHYSIOTHERAPY
State
Year
State
Year
State
Year
AK
1999
LA
1991
NV
1991
AL
1997
MD
2007
NY
1991
AR
1991
ME
1991
OH
1991
CA
1991
MN
1991
OK
1991
CT
1991
MO
1991
OR
1991
FL
2001
MS
1991
SD
1991
HI
1991
MT
1991
TN
1991
IA
1991
NC
1991
TX
1991
ID
1991
NE
1991
UT
1991
IN
1991
NJ
1991
VA
1991
KS
1991
NM
1991
VT
1991
KY
1991
Source: FCLB (1991–2010).
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Any expansion in chiropractors’ clientele or the intensity of services delivered to a particular client may potentially increase earnings. The increase in
earnings may result from the chiropractor delivering a higher-quality service
to the patient, or from the patient’s belief that the service is higher quality. The
increase in earnings may also arise from the chiropractor working more hours.
However, there is disagreement in the labor supply literature over whether the
wage elasticity of labor supply is positive, zero, or slightly negative (Blundell
and MaCurdy 1999). Expanded chiropractic scope of practice may also increase
chiropractor employment. Unemployment is generally very low among medical professionals, but there is variation in the employment-population ratio at
the state level. All of these factors taken together may in turn affect the earnings, hours worked, and employment of physicians and PTs, depending upon the
nature of the relationships of the professions. By expanding access to medical
services, changes to scope of practice may potentially increase consumer welfare. Consumers will have more choice in providers and may be able to obtain
lower prices (either directly from medical professionals or indirectly through
lower insurance premiums). Broader scope of practice may also help further
establish chiropractors in the market for health care.
B. Brief History of Physical Therapy Licensing and “Direct
Access” Laws
Historically, physical therapists have also faced professional conflicts with physicians.7 This conflict was slightly different in nature than the conflict with chiropractors. Allopathic medicine has not been suspicious of the science behind
physical therapy; rather, the profession has viewed physical therapy as treatment that is to be coordinated with other options and managed by physicians.
According to the APTA, physical therapists are “health care professionals who maintain, restore, and improve movement, activity, and health” (APTA
2011, 2). The modern field of physical therapy branched off from the ancient
practice of massage in the early twentieth century (Thornton and Timmons
2013). In particular, the field of physical therapy began to evolve around 1916
with the polio epidemic and in 1917 with the beginning of World War I. There
was a demand for specialized knowledge (including muscle testing and techniques for the restoration of muscle function) that would help those afflicted
7. Treatment methods of PTs and chiropractors overlap a great deal, although there are clear dividing
lines. Some chiropractors believe that subluxation (or misalignment of the vertebrae) is generally the
cause of most health problems. Mainstream chiropractors (or “mixers”) de-emphasize subluxation
and believe in the merits of more conventional medical treatments (Kaptchuk and Eisenberg 1998).
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with polio and rehabilitate wounded soldiers. In 1921, the American Women’s
Physical Therapy Association, now the American Physical Therapy Association
(APTA), was founded.8 In 1955, the role of physical therapy in the healthcare
system was clarified in the Guide to Physical Therapy Practice, which outlines a
physical therapist’s role in the “examination, evaluation, diagnosis, prognosis,
intervention, re-examination, and assessment of outcomes” (APTA 2011, 8).
Similar to the development of licensing in many other professions, physical therapy licensing accelerated shortly after the formation of a professional
association. In 1913, Pennsylvania became the first state to require PTs to obtain
a license. Training requirements for physical therapists have also evolved over
time. Originally, PTs were able to practice after obtaining a bachelor’s degree.
After January 1, 2016, all aspiring physical therapy applicants will be required
to complete a doctorate of physical therapy (DPT) degree. State licensure for
physical therapists is required in all states. Each physical therapist is required
to pass a board-certified exam.
In much of the twentieth century in the United States, PTs were clearly
subordinate to physicians. Patients were only permitted to seek treatment from
PTs after receiving a physician’s referral. In 1957, Nebraska was the first state to
grant PTs direct access to patients, and California followed more than 10 years
later in 1968. Direct access (sometimes referred to as self-referral) means that
a patient may see a PT without a referral. Steps to achieve more independence
began in the 1980s, when APTA adopted a nonreferral policy in which physical
therapy practice was “ethical as long as it was legal in the state” (APTA 2011, 7).
While there has been controversy over the appropriateness of direct access to
PTs, the United States has seen direct-access movements in states with a number of different professions as a reaction to the growth in managed care (e.g.,
direct access to OB/GYNs). Opponents cite concerns that physical therapists
are unable to correctly diagnose a condition such as cancer if the patient has not
first seen a physician. Physical therapists challenge these criticisms, arguing
that physical therapists do not provide a medical diagnosis but rather diagnose
“impairments, functional limitations and disabilities related to medical conditions, movement dysfunction, and other health-related disorders” (APTA 2011,
26). The practice of physical therapy often involves referral to a physician when
necessary. The 1980s and 1990s saw significant expansion of direct-access laws.
At the time of our study, only seven states (Alaska, Hawaii, Indiana, Michigan,
New Mexico, Oklahoma, and Texas) did not permit direct access to PTs. Table 2
8. Men were first admitted and the name was subsequently changed in the late 1930s.
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TABLE 2. PHYSICAL THERAPY DIRECT ACCESS IN THE UNITED STATES IN 2010
State
Year of enactment
State
Year of enactment
AL
None
MT
1987
AK
1986
NE
1957
AZ
1983
NV
1985
AR
1997
NH
1988
CA
1968
NJ
2003
CO
1988
NM
None
CT
2006
NY
2006
DC
2007
NC
1985
DE
1993
ND
1989
FL
1992
OH
2004
GA
2006
OK
None
HI
None
OR
1993
ID
1987
PA
2002
IL
1988
RI
1992
IN
None
SC
1998
IA
1988
SD
1986
KS
2007
TN
1999
KY
1987
TX
None
LA
2003
UT
1985
ME
1991
VT
1988
MD
1979
VA
2001
MA
1982
WA
1988
MI
None
WV
1984
MN
1988
WI
1989
MS
2006
WY
2003
MO
1999
Source: APTA (2016).
contains information on the presence of direct-access laws for PTs across the
United States.9
Like scope-of-practice provisions, direct-access laws may influence the
earnings, hours worked, and employment of PTs, chiropractors, and physicians.
This is especially true for PTs and chiropractors who directly compete with
9. These data are from the American Physical Therapy Association as of 2010.
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each other for clients. In many states, chiropractic organizations are some of
the most vocal critics of PT direct access (Briem et al. 2007). The potential
impact of direct access on the wages of PTs is ambiguous for multiple reasons.
First, public perception of physical therapy may improve with direct-access
laws if patients see direct access as a signal of quality, thereby elevating the
profession and allowing PTs to increase prices. Alternatively, patients may be
suspicious of PT quality in cases where physicians are not making the referral.
Second, direct access increases demand because it removes the constraint of
needing a physician referral; additional patients who would not have received
PT referral under a regime without direct access will now be able to see a PT
under a direct-access regime. PT productivity, however, will still moderate the
wage effect. For PTs that operate with little idle time between patients, only
the price effect will impact wages. Alternatively, for those PTs with idle time
between patients, this increase in demand will unequivocally increase wages—
though, as in the case of chiropractors, labor supply will depend on wage elasticity, which, as noted earlier, is often ambiguous.
C. The Market for Back and Neck Pain Treatment
Presumably chiropractors, physicians, and PTs are all competing for market
share in the $300 billion market for treating back and neck pain. Therefore,
we might surmise that the three professions are substitutes for one another.
A patient experiencing lower back or neck pain will have some choice among
healthcare providers. Patients may have a negative view of chiropractic services, or they may be required to seek referral from a physician to see a physical therapist. The significant changes in chiropractic scope of practice and PT
direct access cause more patients to choose nonphysician treatment for back
or neck pain. Each profession will prescribe a different set of treatments—chiropractors and PTs will generally prescribe less invasive treatments, whereas
physicians will be more inclined to prescribe drugs or surgery (Adams 2014;
Carroll 2010). If chiropractors have a broad scope of practice, patients may
perceive that their services are of higher quality and legitimacy—essentially,
the broad scope of practice serves as a signal. Direct access will allow PTs to
make treatment recommendations first, potentially reducing the amount of
more invasive treatments prescribed by physicians. Chiropractors and PTs are
also likely to compete against each other for clientele because many prospective patients are likely to view them as alternative treatment providers for back
and neck pain based on either word of mouth or previous experience. Furthermore, in the case of orthopedic surgeons, if chiropractor- or PT-directed
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care is effective, it may reduce the downstream need for
surgery. In this regard, chiropractic or PT services could
substitute for surgery, not contemporaneously but across
a patient’s life course.
The relationships between providers, however, may
be more complicated than pure substitution. It is also possible that the three providers may be providing complementary services. In particular, the services provided by
physicians, especially physicians not engaged in general
practice, may complement those provided by PTs and chiropractors. For example, a physician may prescribe surgery for a patient, and the PT may provide rehabilitation
services afterward. In this instance, direct access would
be expected to have little influence on the earnings, hours
worked, or employment of any of the professionals. Alternatively, a patient may consult with a chiropractor or PT
for an initial screening and then ultimately receive treatment from a physician. In this instance, direct access and
broader scope of practice for chiropractors may increase
physician earnings.
Another important factor that influences the market for each of these professional services is insurance
coverage. Following the landmark Wilk decision, chiropractic services were covered by Medicare. Medicaid
coverage is more varied, but Medicaid patients account
for only 1.2–1.5 percent of chiropractor patients in the
United States (Goertz 1996; Hurwitz et al. 1998). Several states have enacted mandates for private insurance
policies to cover chiropractic services. Using data from
Gruber (1994) and annual reports from the Council for
Affordable Health Insurance, we compiled data on when
and if states adopted mandates for insurance coverage
of chiropractic services. Delaware was the first state to
pass a chiropractic mandate in 1963. Seven more states
passed mandates in the 1960s. Twenty-two more states
followed the lead of the federal government and adopted
a mandate in the 1970s. Ten more states passed mandates
in the 1980s, and by 2010 all states except the District of
Columbia, Hawaii, Idaho, and Oregon had mandates for
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“The
relationships
between
providers . . .
may be more
complicated than
pure substitution.
It is also possible
that the three
providers may
be providing
complementary
services.”
chiropractic coverage. We hypothesize that mandated insurance coverage
for chiropractic services should positively affect chiropractor wages, hours
worked, and employment. As for PT services, the 1967 amendments to the
Social Security Act provide for Medicare coverage of outpatient physical
therapy (Cohen and Ball 1968). PT services have historically been held in
higher regard by the greater medical community, and state mandates were
generally not necessary—most private plans began to cover PT services after
1968. Direct access does not seem to have significantly affected the provision
of coverage; research conducted by the APTA suggests that insurers do not
believe direct access is a significant risk factor.
II. LITERATURE REVIEW ON OCCUPATIONAL LICENSING OF
MEDICAL PROFESSIONS
Economic theory suggests that occupational licensing presents a barrier to
entry for particular occupations and thus increases practitioner earnings
(Friedman and Kuznets 1945; Friedman 1962; Stigler 1971). Studies have found
that stricter licensing increases earnings for healthcare occupations such as
dentists (Shephard 1978; Kleiner and Kudrle 2000), radiologic technologists
(Timmons and Thornton 2008), and physicians (Kugler and Sauer 2005). Several studies have examined occupational licensing in the legal literature as
well (for example, Blair and Durrance 2015; Larkin forthcoming). In the area
of chiropractic scope of practice, very little research exists; however, there are
several papers that explore scope of practice in other occupations.
One paper by Perry (2009) examines competition between nurse practitioners (NPs), physician assistants (PAs), and physicians. Perry examines the effect
of granting NPs and PAs the authority to write prescriptions and obtain payment
from insurers on the earnings of each professional. He finds some evidence that
broader scope of practice for NPs increases NP wages and slightly reduces physician wages. His findings also suggest that broader scope of practice for PAs
may reduce NP wages and increase physician wages. A related paper by Stange
(2014) examines the effects of the increasing number of practicing NPs and PAs
on the price and use of healthcare services. Stange’s results suggest that increasing the number of NPs and PAs only impacts patient use in states with more
permissive scope-of-practice legislation for NPs and PAs—an important finding
that highlights the importance of scope-of-practice legislation.
A recent paper by Kleiner and Won Park (2010) examines a related issue
for dentists and dental hygienists. The authors find evidence that hygienists
working in states with more autonomy (or broader scope-of practice legislation)
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earn about 10 percent more and have 5 percent higher employment growth than
their peers. Also, dentists in the same states earn 19 percent less and experience
a 27 percent reduction in dental employment. Like dentists and hygienists, chiropractors, PTs, and physicians may be competing for business or potentially
serving as complements in the medical-service market for back and neck pain.
Although physicians have tightly controlled chiropractor licensing in the past,
their grip has loosened. Thus, our hypothesis would be that the magnitude of the
effects of scope-of-practice differences on chiropractors would be smaller than
the effects found by Kleiner and Won Park (2010). The relationship between
PTs and physicians is probably more similar to that between dentists and dental hygienists. Chiropractors and PTs, however, are more likely to be in direct
competition with one another.
III. DATA
To investigate the effect that scope-of-practice and direct-access legislation has
had on chiropractor, PT, and physician earnings, we use data from the 1970–
2000 census and the 2001–2010 ACS. Since the census does not differentiate
PTs from other therapists (e.g., speech therapists) until 1980, we do not use
1970 data for PTs. The census data is then matched to data on scope of practice
from the Federation of Chiropractic Licensing Boards, as well as direct-access
data from the APTA. All census data are retrieved using Integrated Public Use
Microdata Series (IPUMS) (Ruggles et al. 2010).
We focus on census data from these years for two reasons. First, the greatest changes in chiropractic scope of practice and PT direct access occurred over
this time period. Second, we are not able to identify enough PTs or chiropractors
in the data available from the Current Population Survey (CPS). Summary statistics for the census data are presented in table 3. Hourly wage data are obtained
by dividing annual earnings by reported hours worked per week and reported
weeks worked.10 Wage data are rendered into 2010 dollars using the Consumer
Price Index. All wage data from the census and ACS are subject to top coding—
in other words, there is a cap on the reported salary. Top coding is most likely
to censor physician wages in the early census years (1970 and 1980). This may
create a downward bias in all our estimates of average wages, particularly for
10. For the ACS, weeks and hours worked are available on an interval basis. For the purposes of calculating hourly wages and reporting summary statistics on hours worked, we use the midpoint of the interval provided in the data. Our results are not sensitive to this specification, however—we also performed
regressions using annual earnings (“incwage” in IPUMS), and our main results were largely unchanged.
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TABLE 3. SUMMARY STATISTICS FOR 1970–2000 CENSUS AND 2001–2010 ACS SAMPLES
Chiropractors
Physical therapists
Physicians
Mean
Median
Mean
Median
Mean
Age
43.1
41
37.8
36
45.8
44
Hourly wage (2010$)
41.87
26.40
28.96
25.4
73.93
56.20
Usual hours worked
35.1
40
34.6
40
49.1
Female
Median
50
Mean (%)
Mean (%)
Mean (%)
25.8
33.4
74.0
African American
1.7
4.8
3.6
Other minority
9.5
9.0
16.6
Hispanic
3.5
4.4
5.0
Masters
6.3
20.8
0
Doctorate
19.7
3.2
100
N
7,012
34,630
129,049
Notes: All data are taken from 1970, 1980, 1990, and 2000 US census and 2001–2010 ACS and retrieved using Ruggles
et al. 2010. The PT sample does not include observations from 1970.
physicians.11 Table 3 reveals a few items of interest. First, physicians are paid
significantly more than chiropractors and PTs. We should again point out that
we are unable to separate general practitioners from specialists or surgeons;
physicians are broadly defined as those who diagnose or treat injuries and illnesses in patients. It should be noted, though, that physicians work more hours
and also are required to obtain a doctoral degree in medicine. Additionally, the
professions are split along gender lines: PTs are primarily female, but physicians
and chiropractors are mostly male.
IV. EMPIRICAL MODEL
Our approach is to estimate models using two-way fixed effects. To empirically examine the effects of changes in scope of practice and direct access on the
earnings of each professional i in state s at time t, we estimate the following wage
equation (in natural log) for chiropractors, physicians, and PTs respectively:
ln(hourlywageist) = α + β(Lst) + δ(Tt) + ξ(Ss) + ϕ(Yist) + εist,(1)
11. Top coding may also result in a downward bias in our estimated coefficients of the effects of
broader scope of practice for chiropractors and direct access for PTs and physicians. Our empirical
estimates for physicians should therefore be considered a conservative lower bound of the magnitude
of the effect.
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where L is a vector of variables measuring changes in licensing legislation for
chiropractors and PTs, T is a vector of year fixed effects, S is a vector of state
fixed effects, and Y is a vector of individual characteristic indicator variables
(e.g., age, education, ethnicity, gender, and race). Education is measured using
a dummy variable for whether the respondent has completed a master’s or doctoral degree. Ethnicity is measured using a Hispanic-origin dummy variable.
Gender and race are measured using similar dummy variables (for females,
African Americans, and other minorities). The rationale for each variable is
explained below.
We use a similar, nonlogged equation to estimate the effects of scope of
practice and direct access on hours worked for each profession. We also estimate
the effects of scope of practice and direct access (Lst) on state-level employment
population estimations. Because these models are at the state level, we include
state and year fixed effects but no individual-level control variables.
We measure L using two state-level variables. The chiropractor scopeof-practice index variable ranges in value from 0 to 3 and counts the number
of procedures (phlebotomy, physiotherapy, or discussion about prescribing
proprietary drugs) state s allows chiropractors to perform at time t. The directaccess variable equals 1 if state s grants PTs direct access to patients at time
t, where t is the census year. We also perform regressions to test for duration effects for direct access (including a continuous variable indicating the
number of years since the change in licensing law), given that some studies
have found that the effects of changes in occupational licensing laws are not
realized immediately (Thornton and Timmons 2013). We hypothesize that
the chiropractic scope-of-practice variable and direct-access variable should
have positive coefficients for the wages of chiropractors and PTs, respectively.
As for the other coefficients, the sign (positive or negative) will depend upon
the nature of the relationship between the professionals. We suspect that chiropractors and PTs are in direct competition with one another for patients
and should be substitutes. Thus, the sign of our chiropractic scope-of-practice
variable should be negative for PTs, and the sign of the direct-access variable
should be negative for chiropractors. The relationship between physicians and
the other two professions is more complex—it is not clear how direct access
may affect the relationship. Primary-care physicians may compete with chiropractors and PTs for patients experiencing back and neck pain. But without
direct access, PTs are clearly complementary with physicians. Looking more
broadly at all physicians including specialists, chiropractors are more likely to
serve as complements.
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As for weekly hours worked and employment, we suspect that expanded
scope of practice and direct access would increase the hours worked of chiropractors and PTs. It is also possible, however, that after the passage of each
law, patients may perceive that the quality of services being offered by each
practitioner improves. Practitioners may have the ability to charge higher fees
and therefore choose to work fewer hours. Employment may also be affected if
changes in the level of competition influence demand for the professions.
As noted in preceding sections, there are differences across states and
over time in whether or not private insurers are required to cover chiropractic
care. This requirement is likely to have a positive relationship with chiropractor wages and may have a positive or negative effect on PT and physician wages
depending on the nature of the relationship between the professions. We control for this factor in the estimation of equation (1). All estimations include census weights. Standard errors in these estimations are clustered at the state level.
V. EMPIRICAL FINDINGS
A. Impacts on Wages
Table 4 contains the results of our estimations of equation (1) for wages for
each of the three occupations. Columns (1) and (2) contain the results of the
specifications estimating the effect of the policies on the natural log of chiropractor wages, with one specification including PT direct access as a binary
measure and a second including the duration of direct access as the measure.12
Similarly, columns (3) and (4) model the natural log of physician wages as the
dependent variable, while columns (5) and (6) model the natural log of PT
wages as the dependent variable. Beginning with chiropractors, we do find
some evidence that chiropractors earn more if they work in states that have
more expansive scope-of-practice laws, as measured by the scope-of-practice
index (7.2–8.6 percent per task allowed).13 Broader scope of practice may
allow chiropractors to attract more patients. Performing routine medical services usually done by physicians or in outpatient clinics may signal to potential
patients that the services being offered by chiropractors are legitimate. There
is also some evidence that chiropractors may face competition from PTs,
as direct-access duration correlates with reduced chiropractor wages. The
12. The sample size changes in the table owing to the inclusion of education controls forcing the
removal of 1970 census data.
13. Coefficients are converted to percentages using the 1−eb transformation.
M ERC ATUS CENTER AT GEORGE MA SON U NIVERSIT Y
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TABLE 4. TWO-WAY FIXED EFFECTS ESTIMATES OF THE EFFECTS OF SCOPE OF PRACTICE AND
DIRECT ACCESS ON CHIROPRACTOR, PHYSICIAN, AND PT WAGES (LOG WAGES)
Chiropractor wages
Scope-of-practice
index
DA dummy
(1)
(2)
0.0823**
0.0696**
(0.0317)
(0.0314)
0.0364
(3)
(4)
0.0055
0.0054
(0.00883)
(0.00882)
−0.0014
(0.0462)
Duration DA
Physician wages
Physical therapist wages
(5)
(6)
−0.0171
−0.0167
(0.0127)
(0.0129)
0.0089
(0.0090)
(0.0152)
−0.0073**
−0.0000
0.0000
(0.0033)
(0.0000)
(0.0000)
Chiro insurance
−0.0691
−0.0767
0.0223
0.0221
−0.0097
mandate
(0.104)
(0.104)
(0.0169)
(0.0172)
(0.0303)
−0.0092
N
7,012
7,012
129,046
129,046
34,630
34,630
R2
0.16
0.16
0.34
0.34
0.17
0.17
(0.0308)
Notes: *p-value < 0.1; **p-value < 0.05; ***p-value < 0.01. Standard errors are clustered at the state level. All data are
drawn from 1970–2000 US census and 2001–2010 ACS and retrieved using Ruggles et al 2010. All regressions use
individual controls that include age, age-squared, female dummy, minority dummy variables, and Hispanic dummy
variable, as well as whether the individual had a master’s or PhD.
effects of both scope-of-practice and direct-access laws on physician wages
are small and imprecisely estimated. Our inability to separate physicians of
different specializations in the census and ACS may be driving this result.
Turning our attention to PTs in columns (5) and (6), we find point estimates
suggesting that chiropractors and PTs are substitutes, but these estimates
are not precise. Direct-access laws do not have the same effects on PT wages
that expanded scope of practice does for chiropractors. It is possible that our
inability to estimate an effect of direct access on PT wages could be owing to
the canceling of competing effects—direct access may potentially improve or
reduce patient perceptions of quality. It is also possible that direct access is
less impactful because the population that would use PT may be conditioned
to seek treatment at a physician’s office first.14
B. Impacts on Hours Worked and Employment
To better understand the mechanism for the wage effects we have esmated,
we now estimate the effects of chiropractic scope of practice on hours worked
14. We also performed regressions estimating the effect of expanded chiropractic scope of practice
and PT direct access on labor market outcomes for occupational therapists (OTs). We found no evidence of any measurable labor-market effects on the OTs from these changes.
M ERC ATUS CENTER AT GEORGE MA SON U NIVERSIT Y
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and employment in each profession. Tables 5 and 6 report the results of these
estimations. The sample sizes for each profession here are larger—survey
respondents sometimes report hours worked but not earnings. Expansion of
chiropractors’ scope of practice decreases hours worked per week by approximately one hour. Taken together with our results in table 4, this slight decrease
in weekly hours worked indicates that broad chiropractor scope of practice
enhances patient perceptions of the quality of service. Chiropractors are not
working more hours, but they are able to earn higher wages, suggesting that
the increase in wages is a result of chiropractors’ ability to charge higher fees.
We also find some evidence that direct access has resulted in fewer hours
worked for chiropractors (column (2)), again suggesting that they are potential substitutes. We should note that the each of the estimated effects is quite
small—changes in scope of practice and direct access do not appear to have
a large effect on the number of hours that chiropractors work. We find little
evidence that physicians’ hours worked are affected by changes in scope of
practice or direct access.
In table 6, we find very little evidence that scope of practice and direct
access have affected the employment population ratio of any of the professions.
This result is not surprising in the case of physicians because training is long and
supply responses take time. Furthermore, the competition from alternative providers like chiropractors and PTs is not a deterrent to entry into the profession.
In our previous regressions, we used an index to estimate the effects of
changes in chiropractic scope of practice. We found little evidence that changes
in scope of practice have affected the wages of PTs or physicians. In table 7, we
disaggregate the index of chiropractic scope of practice and construct individual dummy variables for phlebotomy, physiotherapy, and advice regarding
proprietary drugs. We continue to find little evidence that changes in chiropractic scope of practice have affected physician wages. We find some evidence
that allowing chiropractors to prescribe proprietary drugs is associated with
approximately 4 percent lower PT wages . This result is consistent with the
theory that PTs and chiropractors are substitute providers of care. We continue
to find little evidence (results not reported) that changes in chiropractic scope
of practice are affecting hours worked or employment of PTs or physicians.
C. Policy Endogeneity
To assess whether these policies are potentially endogenous, we examined
whether wage or supply growth rates in the preceding intercensal period
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TABLE 5. TWO-WAY FIXED EFFECTS ESTIMATES OF THE EFFECTS OF SCOPE OF PRACTICE AND
DIRECT ACCESS ON CHIROPRACTOR, PHYSICIAN, AND PT HOURS WORKED
Chiropractor hours
(1)
(2)
Physician hours
(3)
(4)
Scope-of-practice
−0.925*
−1.108**
−0.160
−0.161
index
(0.489)
(0.432)
(0.180)
(0.183)
DA dummy
0.155
−0.0300
(0.389)
Duration DA
(6)
0.0456
0.0388
(0.238)
(0.235)
(0.158)
−0.0001
(0.0331)
Chiro insurance
(5)
0.0614
(0.159)
−0.0786**
Physical therapist hours
0.0001
(0.0001)
(0.0001)
0.936
0.856
−0.228
−0.240
−0.199
−0.180
mandate
(0.580)
(0.642)
(0.460)
(0.463)
(0.340)
(0.339)
N
12,735
12,735
151,083
151,083
36,260
36,260
R2
0.13
0.13
0.01
0.01
0.18
0.18
Notes: *p-value < 0.1; **p-value < 0.05; ***p-value < 0.01. Standard errors are clustered at the state level. All data are
drawn from 1970–2000 US census and 2001–2010 ACS and retrieved using Ruggles et al 2010. All regressions use
individual controls that include age, age-squared, female dummy, minority dummy variables, and Hispanic dummy
variable, as well as whether the individual had a master’s or PhD.
TABLE 6. TWO-WAY FIXED EFFECTS ESTIMATES OF THE EFFECTS OF SCOPE OF PRACTICE AND
DIRECT ACCESS ON CHIROPRACTOR, PHYSICIAN, AND PT EMPLOYMENT POPULATION RATIOS
# Chiropractors/million
(1)
Scope of practice
−16.41
index
(14.75)
DA dummy
−27.89
(2)
−7.120
(14.94)
−41.71
(51.59)
mandate
−52.33
(51.69)
# Physical therapists/million
(5)
−5.543
(29.10)
(6)
−0.884
(29.58)
18.07
(68.26)
2.421
(38.71)
−5.356
(1.505)
Chiro insurance
(4)
78.05
(21.09)
Duration DA
# Physicians/million
(3)
3.129
(4.782)
(3.201)
24.42
27.20
43.38
62.47
−54.30
−53.20
(44.77)
(44.70)
(91.59)
(91.18)
(55.63)
(55.16)
N
675
675
714
714
661
661
R2
0.41
0.41
0.67
0.67
0.54
0.54
Notes: *p-value < 0.1; **p-value < 0.05; ***p-value < 0.01. Standard errors are clustered at the state level. All data are
drawn from 1970–2000 US census and 2001–2010 ACS and retrieved using Ruggles et al 2010. All regressions use
individual controls that include age, age-squared, female dummy, minority dummy variables, and Hispanic dummy
variable, as well as whether the individual had a master’s or PhD.
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TABLE 7. TWO-WAY FIXED EFFECTS ESTIMATES OF THE EFFECTS OF SCOPE OF PRACTICE AND
DIRECT ACCESS ON PHYSICIAN AND PT WAGES (LOG WAGES)
PT wages
Phlebotomy dummy
Physiotherapy dummy
Proprietary drugs dummy
DA dummy
Physician wages
(1)
(2)
−0.0183
−0.020
(0.0300)
(0.0289)
0.00298
0.00254
(3)
0.0253
0.0257
(0.0259)
(0.0259)
0.0116
0.0114
(0.0172)
(0.0171)
(0.0170)
(0.0167)
−0.0390*
−0.0400*
−0.00447
−0.00437
(0.0205)
(0.0203)
(0.0154)
(0.0151)
0.00942
−0.00161
0.0146
Chiro insurance
mandate
(4)
−0.0100
0.0296
(0.00861)
−0.00995
0.0195
0.0196
0.0297
(0.0172)
(0.0173)
N
34,630
34,630
129,046
129,046
R2
0.16
0.16
0.24
0.24
Notes: *p-value < 0.1; **p-value < 0.05; ***p-value < 0.01. Standard errors are clustered at the state level. All data are
drawn from 1970–2000 US census and 2001–2010 ACS and retrieved using Ruggles et al 2010. All regressions use
individual controls that include age, age-squared, female dummy, minority dummy variables, and Hispanic dummy
variable, as well as whether the individual had a master’s or PhD.
predict policy adoption in the most recent intercensal period. As a specific
example using chiropractic, we estimated the following regression:
Δ SOP INDEX s,t = α0 + α1 Chiropractic wage growth/capita s,(t−1) +
α2 Chiropractor supply growth/capita s,(t−1) +
α3 Physician wage growth/capita s,(t−1) +
α4 Physician supply growth/capita s,(t−1) +
α5 ΔX s,t + α6 Chiro colleges,(t−1) + us,t, (2)
where the dependent variable is the change in the state-level chiropractic
scope-of-practice (SOP) index between the previous and current census, and
chiropractic and physician wage and supply growth are in the lagged intercensal period. X is a vector of the change in characteristics of the population used
in our main regression during the intercensal period, and “Chiro college” is an
indicator variable capturing the presence of a chiropractic college in the state
in the previous census.
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TABLE 8. ESTIMATES OF THE EFFECTS OF WAGE AND SUPPLY GROWTH ON POLICY ADOPTION
ΔSOP index
Mean = .544
Adoption of DA
Mean = .145
Growth in chiropractor
−.00019
Growth in physical therapist
−.00014
wages
(.00033)
wages
.00107**
Growth in physical therapists
(.00052)
per capita
Growth in chiropractors
per capita
Growth in physician
(.00053)
−.00010
(.00020)
.00335
Growth in physician
.00048
wages
(.00232)
wages
(.00140)
Growth in physicians
−.00060**
Growth in physicians
.00011
per capita
(.00027)
per capita
(.00143)
Chiropractic college
−.00712
Physical therapy program
.06796
N
(.16075)
(.12200)
112
101
Notes: *p-value < 0.1; **p-value < 0.05; ***p-value < 0.01. Models include state-level changes in the age, the proportion female, racial/ethnic composition, and education of the chiropractors and physical therapists in the most recent
intercensal period. Because of missing data, some state-year observations are not included in the regression.
This estimation allows us to examine many of the factors raising endogeneity concerns. First, states that expand chiropractors’ scope of practice may do so in
response to growing demand for these services. The demand shift would, of course,
increase wages in advance of policy adoption unless supply shifted by the same
amount. By including both wage and supply growth among chiropractors in the
prior period, the model is intended to estimate whether demand is in fact growing.
Further, the chiropractic college variable acts as a proxy for the profession’s political power in a state because having an institution of higher education in the chiropractic field may indicate broad support for the profession. Conversely, physician
wage growth or supply growth in the prior period may impact the extent to which
physicians, who typically occupy a majority of seats on state medical regulation
boards, would fight scope-of-practice expansion for competing professions.
We also estimated an analogous model where we examined physical
therapy direct-access law adoption in the most recent intercensal period and
substituted lagged physical therapy wage and supply growth and presence of
accredited physical therapy training programs for the chiropractor variables.
The results of these estimations are in table 8. Chiropractic scope of practice expanded by about 0.54 on average in an intercensal period. Increases in
chiropractic supply widened the scope of practice. The average growth in the
number of chiropractors in the intercensal periods was 147 per million residents.
Thus, if a particular state had experienced the average increase in the number
of chiropractors in one intercensal period, the state would have increased its
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“Consumer
welfare is likely
to be improved
by having greater
access to lowerpriced care and
more choices for
pain treatment.”
scope-of-practice index by 0.16 in the subsequent intercensal period—about 1/5 of a standard deviation at the mean.
Conversely, an increase of 212 physicians per million residents (the mean intercensal increase in physician supply)
would lead to a 0.16 standard-deviation decrease in the chiropractic scope-of-practice index in the state in the subsequent intercensal period. There is, however, no discernible
effect of lagged wage increases on contemporaneous policy.
Thus, the most likely explanation of these effects is that the
changes in supply per population are shifting the balance
of power among the professions and thus affecting subsequent scope-of-practice changes (or lack thereof ). We
therefore believe that our estimated effects of chiropractic
scope-of-practice changes on the labor market are likely
conservative estimates—scope of practice and chiropractor supply are likely to be increasing simultaneously.15
In contrast to the scope of practice for chiropractors, we find no evidence that any of the lagged factors that
might predict policy adoption had an effect on PT directaccess policy adoption.
VI. CONCLUSION
In this paper, we have examined the influence of changes
in scope-of-practice and direct-access laws on the wages,
hours worked, and employment of chiropractors, physical therapists, and physicians. Broader scope of practice
seems to be associated with higher chiropractor wages.
We also find evidence that expanded scope of chiropractor practice slightly reduces the average number of hours
chiropractors work per week. In sensitivity checks, we find
15. It is possible that our estimation of the effect of changes in scope of practice could be capturing a change in demand for chiropractic services unrelated to changes in scope of practice. We believe that this is unlikely for at
least two reasons. First, market changes are not likely to be as impactful
without accompanying changes in regulation—as noted by Stange (2014) in
the market for nurse practitioners and physician assistants. Second, patient
preferences are very slow to adjust to new practitioners in the healthcare
market. Half of Americans still prefer to receive care from a physician
rather than an alternative healthcare provider (Dill et al. 2010).
M ERC ATUS CENTER AT GEORGE MA SON U NIVERSIT Y
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that lagged increases in the supply of chiropractors lead to expanded scope of
practice but that increases in the supply of physicians restrain this expansion.
These results suggest our estimates of the wage effects of expanded scope of
practice represent a lower-bound estimate. Expanded chiropractic scope of
practice seems to affirm that PTs and chiropractors serve as substitutes in the
market for pain treatment. We also find some evidence that expanded chiropractor scope of practice may be associated with lower PT wages.
Physical therapy direct-access laws do not seem to affect PT, physician,
or chiropractor wages. We find some evidence that direct-access laws may be
reducing chiropractors’ hours worked. With the data used in our study, we can
only speculate why PT direct access is not having a substantial effect. It is possible that patients continue to prefer to see doctors despite changes in the law.
We also find little evidence that expanded chiropractor scope of practice or
PT direct access has affected employment of chiropractors, physicians, or PTs.
The changes in competition do not appear to substantially affect entry into
any of the three professions. In the ongoing search for ways to reduce onerous
healthcare costs in America, our study may guide policy making. Neither PTs
nor chiropractors are perfect substitutes for primary-care physicians. In certain instances, such as when patients are experiencing neck or lower back pain,
patients may receive better-quality care at lower prices by seeing a chiropractor
or PT as opposed to a physician. Consumer welfare is likely to be improved by
having greater access to lower-priced care and more choices for pain treatment.
Expanding the scope of practice for mid-level healthcare providers such as
chiropractors and PTs may potentially improve the efficiency of the healthcare
market in the United States.
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ABOUT THE AUTHORS
Dr. Edward J. Timmons is an associate professor of economics and director of
the Center for the Study of Occupational Regulation at Saint Francis University.
His research has been published in the Journal of Law and Economics, the British Journal of Industrial Relations, the Journal of Labor Research, Monthly Labor
Review, Eastern Economic Journal, and the European Journal of Comparative
Economics. He has published several papers for the Mercatus Center at George
Mason University and has also contributed several op-eds to U.S. News & World
Report, USA Today, the Tampa Bay Times, the Louisville Courier-Journal, and
Nashville’s Tennessean. His research has been cited in scholarly journals, in the
popular press, by the White House, and in a Senate hearing on occupational
regulation. Timmons has presented his research across the United States and
in the United Kingdom and Italy. He has worked as a visiting research fellow at
the Collegio Carlo Alberto in Moncalieri, Italy.
Dr. Jason M. Hockenberry is an associate professor in the Department of
Health Policy and Management at Emory University’s Rollins School of Public
Health. He is a healthcare economist with a specific interest in the effects of
policy on quality and efficiency of health services delivery. His work has been
published in the Journal of Health Economics, Health Affairs, Industrial and
Labor Relations Review, Journal of Economics and Management Strategy, and
numerous leading medical journals.
Dr. Christine Piette Durrance is an associate professor in the Department
of Public Policy at the University of North Carolina at Chapel Hill. She is an
applied microeconomist with specific interests in health economics and health
policy. Her work has been published in the Journal of Health Economics, American Journal of Health Economics, Health Services Research, Social Science and
Medicine, and JAMA Pediatrics.
ACKNOWLEDGMENTS
The authors would like to thank Morris Kleiner, Jim Burgess, John Perry, and
other participants at the 2015 Labor and Employment Relations Association
session “Employment Relations in the Healthcare Setting” at the American
Economic Association Annual Meetings in Boston and the 2014 conference on
employment relations in the healthcare setting at Rutgers University.
ABOUT THE MERCATUS CENTER AT GEORGE MASON UNIVERSITY
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­university source for market-oriented ideas—bridging the gap between academic ideas and real-world problems.
A university-based research center, Mercatus advances knowledge about
how markets work to improve people’s lives by training graduate students, conducting research, and applying economics to offer solutions to society’s most
pressing ­problems.
Our mission is to generate knowledge and understanding of the institutions that affect the freedom to prosper and to find sustainable solutions that
overcome the barriers preventing individuals from living free, prosperous, and
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Founded in 1980, the Mercatus Center is located on George Mason University’s Arlington and Fairfax campuses.